The invention relates to a metal-clad, compressed-gas insulated, high-voltage switching station with an insulated grounding switch whose housing is flange-mounted to the casing of the high-voltage switching station by way of flanges and fixing agents which connect these flanges, whereby one insulating ring is mounted gastight between both flanges. On the inside of this insulating ring, an annular electric conductor, which is provided with a terminal lug, is embedded such that the terminal lug which runs outside passes radially through the insulating ring, and the annular part of the conductor surrounds the contact pin of the grounding switch with clearance, whereby the conductor bears a sliding contact by way of which it is electrically connected to the contact pin.
This type of an insulated grounding switch for a metal-clad, compressed-gas insulated, high-voltage switching station is known from the teachings of U.S. Pat. No. 3,778,374. The conductor, with the terminal lug running to the outside, which is embedded in the insulating ring can be either grounded via this grounding switch or a voltage can be applied to it which is then transferred to the contact pin of the grounding switch in order to implement testing. In the known grounding switch, the annular part of the conductor is embedded on the inside of the insulating ring. This insulating ring reposes between the flange of the housing of the grounding switch and the flange of the casing of the high voltage switching station and is penetrated by the fixing agents which serve to fasten the grounding switch to the high voltage switching station. In this manner, the insulating ring is pressurized by the compression forces required for fastening it and is thereby mechanically stressed by high compressive forces.
Consequently, the tightening torques for the fixing agents must be stipulated precisely and with a narrow tolerance range in order to avoid overloading the insulating material. Furthermore, the fixing agents must be provided with an insulation since they are located in the immediate vicinity of the embedded conductor and are connected to the grounded casing. The entire outer surface area of the insulating ring is furthermore exposed. In the case of outdoor use, this can create problems since then the insulating property of the insulating ring can be impaired by deposits.